ASTM A268 TP430 Seamless Stainless Steel Tube

Overview of ASTM A268 TP430

ASTM A268/A268M covers seamless and welded ferritic and martensitic stainless steel tubes for general and high-temperature service. TP430 (UNS S43000) is a 16-18% chromium ferritic grade with very low nickel content and is non-hardenable by heat treatment. It combines good mechanical properties with oxidation resistance and is widely used in architectural decoration, kitchen equipment, automotive exhaust components, HVAC ducts and industrial fluid conveying systems.

Chemical Composition

Composition limits per ASTM A268/A268M; the EN equivalent designation is 1.4016 (X6Cr17) and the JIS designation is SUS430.

Element (wt %)	TP430 (S43000)
Carbon, max	0.12
Manganese, max	1.00
Phosphorus, max	0.04
Sulfur, max	0.03
Silicon, max	1.00
Chromium	16.0-18.0

Mechanical Properties

Annealed condition, minimum values per ASTM A268/A268M.

Property	TP430 (S43000)
Tensile strength, min (ksi / MPa)	60 / 415
Yield strength, min (ksi / MPa)	35 / 240
Elongation in 2 in (50 mm), min (%)	20
Hardness, max	90 HRB / 190 HBW

Manufacturing, Testing and Inspection

Seamless tubes are produced by extrusion or piercing of solid billets to achieve a uniform cross-section without longitudinal welds, giving uniform wall thickness and a smooth inner surface for efficient fluid conveyance. Welded tubes are produced from strip with a longitudinal fusion weld. Tubes are delivered solution annealed and pickled. Testing per ASTM A268/A268M and A1016/A1016M includes hydrostatic or non-destructive electric testing, tension testing, flaring testing for seamless tubes, flange testing for welded tubes, hardness testing, reverse flattening testing and intergranular corrosion testing. Marking per A1016/A1016M records the standard, grade, size, heat number and batch number, and states whether the tube is hot-worked or cold-worked.

Applications and Grade Selection

Typical applications include architectural decoration tubes, kitchen equipment, automotive exhaust auxiliary components, HVAC ducts and industrial fluid conveying systems. TP430 is ferritic and therefore magnetic, with lower ductility and toughness than austenitic grades; it is not intended for heavily chloride-corrosive or cryogenic service. It offers oxidation resistance at temperatures up to approximately 816°C (1500°F), and its extremely low nickel content makes it a cost-effective alternative to austenitic stainless steels such as 304 where the corrosion requirements are moderate. Selection between TP430 and 304 should consider corrosion, forming, welding and cost on a project basis.

Frequently Asked Questions

Q1. What is TP430 stainless steel?
A ferritic stainless steel with 16-18% chromium and very low nickel, designated UNS S43000 and covered by ASTM A268/A268M.

Q2. What is the difference between TP430 and 304?
TP430 is ferritic, magnetic and low-nickel, while 304 is austenitic with 8-10.5% nickel; 304 offers higher toughness and better corrosion resistance, and TP430 is generally lower in cost.

Q3. Is TP430 magnetic?
Yes. Ferritic stainless steels are magnetic, unlike fully annealed austenitic grades.

Q4. What is the maximum service temperature?
TP430 provides oxidation resistance up to approximately 816°C (1500°F) in air.

Q5. Can TP430 be welded?
Yes, but with low heat input and suitable filler to limit grain growth in the heat-affected zone; the grade is non-hardenable by heat treatment.

Q6. Which standards apply to TP430 tube?
ASTM A268/A268M for seamless and welded tube, with testing per ASTM A1016/A1016M; EN 1.4016 and JIS SUS430 are equivalent designations.